Is there no way you can talk to one of the guys you're training with and say, "hey, let's go at it a little harder for once?" I'm no grappling guy, but from my experience, both hard and light sparring have their merits and - yeah, I know this sounds very generic - the balance seems kind of important.

edit: If I'm completely oblivious to some of the serious grappling business I'll be pleased to be enlightened.

Personally, I divide it up a little differently. I consider it more of a mobility based game vs. a pressure based game, with intensity as a separate component applicable to both. Depending on the size, strength, and attributes of my opponent, I may decide to use one or the other game.

If the opponent is significantly smaller and faster than myself, I'm more likely to try to apply heavy pressure as an attempt to limit their mobility. Conversely, if the person is much larger and stronger than myself, I'm more likely to try to remain mobile and exploit their probable reactions. However, regardless of which strategy employed, I'm still consistently trying to improve my position and submit my opponent.

Going balls out constantly at the expense of technique is spazzing, but constantly going at low intensity and asking your training partners to the do the same is laziness.